Video duplication control system, video playback device, video recording device, information superimposing and extracting device, and video recording medium

ABSTRACT

A playback device 10 generates a PN code with a start timing based on a video sync signal, and generates a PN inverse code which has a reverse polarity to that of the PN code with a timing based on the video sync signal. An anti-duplication control signal is spectrally spread using this PN code, superimposed on the video signal and supplied to a recording device. A PN inverse code which is the same as the PN inverse code used in the playback device is also generated in the recording device based on the video sync signal, and reverse spectral spread is performed using this PN inverse code.

BACKGROUND OF THE INVENTION

[0001] This invention relates to a video duplication control system forplaying back a video signal recorded on a recording medium, and limitingor preventing the reproduced video signal from being played back andrecorded on another recording medium. It also relates to a videoplayback device, video recording device and video recording medium onwhich a video signal is recorded which use this video duplicationcontrol system.

[0002] VTR (Video Tape recording devices) are a commonplace feature ofmodern-day life, and many kinds of software exist which can be playedback on a VTR. Digital VTR or DVD (Digital Video Disks) playback devicesare now a reality, and provide videos and sound of exceptionally highquality.

[0003] There is, however, a problem in that this great abundance ofsoftware can be copied without restriction, and several methods havealready been proposed to prohibit this.

[0004] For example, for a VTR which outputs an analog video signal, onemethod to prevent copying uses a difference in the AGC (Automatic GainControl) system, or in the APC (Automatic Phase Control) system, of theVTR recording device and of a monitor receiver which displays the video.

[0005] When the VTR employs AGC using a pseudo sync signal inserted inthe video signal, a monitor receiver employs AGC which does not use thispseudo sync signal. In this anti-duplication method using a differencein the type of AGC, a very high level pseudo sync signal is inserted andoutput in the video signal supplied from the playback VTR to therecording VTR as an AGC sync signal.

[0006] When the VTR employs APC using the phase of a color burst in thevideo signal, the monitor receiver uses a different type of APC. In ananti-duplication method using a difference in the type of APC, the phaseof the color burst in the video signal supplied from the playback VTR tothe recording VTR is partially reversed.

[0007] The monitor receiver which receives the analog video signal fromthe playback VTR plays back the video correctly without being affectedby the high level pseudo sync signal in AGC or the partial phasereversal of the color burst signal in APC.

[0008] On the other hand, when a VTR records, on a recording medium, theanalog video signal into which pseudo sync signals have been inserted orthe analog video signal which has been subjected to color burst signalphase reversing control in the playback VTR as described hereabove,proper gain control or phase control based on the input signal cannot beperformed, and so the video signal is not correctly recorded. Even ifthis signal is played back, therefore, normal picture and sound cannotbe obtained.

[0009] In the case of a digitized video signal, e.g. in a digital VTR,an anti-duplication signal or an anti-duplication control signalcomprising for example a duplication ranking control code, is added asdigital data to the video signal and recorded on the recording medium,so as to prevent or control duplication of the video.

[0010] In this case, the playback digital VTR reads the video signal,audio signal and anti-duplication control signal, and supplies them asdigital or analog data to a recording digital VTR.

[0011] In the digital VTR being used as a recording device, theanti-duplication control signal is extracted from the supplied playbacksignal, and recording of the playback signal is then controlled based onthe anti-duplication control signal. For example, when theanti-duplication control signal comprises an anti-duplication signal,the recording VTR does not perform recording.

[0012] Alternatively, when the anti-duplication control signal comprisesa copy ranking control code, recording is controlled by this rankingcontrol code. For example, when the copy ranking code limits duplicationto one copy, the digital VTR used for recording adds thisanti-duplication code before recording the video signal and audio signalon the recording medium as digital data. It is thereafter impossible toduplicate the video signal from the copy.

[0013] Hence, in the case of a digital connection when the video signal,the audio signal, and the anti-duplication control signal used asdigital signals are supplied to the digital VTR used as a recordingdevice, anti-duplication control is performed on the recording sideusing the anti-duplication control signal by supplying this signal tothe digital VTR as digital data.

[0014] However, in the case of an analog connection where the videosignal and audio signal are supplied as analog signals, theanti-duplication control signal is lost when the signal supplied to therecording device is D/A converted. Hence, in the case of an analogconnection, an anti-duplication control signal must be added to the D/Aconverted video or sound signal, and this causes deterioration of thevideo signal and audio signal.

[0015] It is, therefore, difficult to add an anti-duplication controlsignal and to extract it in the recorder for the purpose ofanti-duplication control, without causing deterioration of the D/Aconverted video signal or audio signal.

[0016] Conventionally, therefore, in the case of an analog connection,duplication was prevented by an anti-duplication method using adifference in the AGC, or a difference in APC characteristics, betweenthe VTR and the monitor receiver as described hereabove.

SUMMARY OF THE INVENTION

[0017] However, in some cases, when anti-duplication is prevented usingthe aforesaid difference in the AGC or a difference in APCcharacteristics between the VTR and the monitor receiver, depending onthe type of AGC or APC characteristics on the recording side, the videosignal may nevertheless be correctly recorded. In this case, it mighthappen that duplication cannot be prevented, or that the reproducedvideo on the monitor receiver is distorted. Further, it was troublesometo change over the anti-duplication method depending on whether therewas an analog connection or a digital connection.

[0018] The inventors have already proposed an anti-duplicationprevention method in which a spectrally spread anti-duplication controlsignal is superimposed on a video signal (U.S. patent application Ser.No. 08175510). This method may be used for both digital connections andanalog connections, and it causes no deterioration of the video or soundwhich is played back.

[0019] According to this method, when the original recording medium isfabricated, a PN (Pseudorandom Noise) sequence code (referred tohereafter as PN code) used as a spread code is generated with asufficiently fast period and spectrally spread by applying it to theanti-duplication control signal. In this way, a narrow bandwidth, highlevel anti-duplication control signal is converted to a wideband, lowlevel signal which does not affect the video signal or sound signal.This spectrally spread anti-duplication control signal is thensuperimposed on the video signal supplied to the recording medium, andrecorded.

[0020] On the recording side, a PN code is generated with the sametiming and phase as the PN code used for spectral spread in the playbackdevice relative to the video signal supplied by the playback device. Thegenerated PN code is applied to the video signal on which theanti-duplication control signal is superimposed so as to extract theoriginal anti-duplication control signal, i.e. so as to perform reversespectral spread. Anti-duplication is then controlled based on theanti-duplication control signal extracted by reverse spectral spread.

[0021] In this way, the anti-duplication control signal is spectrallyspread and superimposed on the video signal as a wideband, low levelsignal in the playback device. It is therefore difficult for a personwishing to illegally duplicate the video signal, to remove theanti-duplication control signal which is superimposed on it.

[0022] However, it is possible for a person aiming to prevent illegalduplication to detect the superimposed anti-duplication control signalby reverse spectral spread, and use it. This anti-duplication controlsignal is therefore supplied to the recording device together with thevideo signal. On the recording side, the anti-duplication control signalis detected, and duplication is precisely controlled according to thedetected anti-duplication control signal.

[0023] According to this method, as described hereabove, the spectrallyspread anti-duplication control signal is superimposed as a wideband,low level signal on the video signal, but it must be superimposed at alower S/N ratio than that of the video signal in order for the videosignal not to cause deterioration of the video signal.

[0024] To superimpose the spectrally spread anti-duplication controlsignal at a lower S/N ratio than that of the video signal, and to beable to detect the anti-duplication control signal superimposed on thevideo signal in the recording device, the number of the PN code (PN codelength) required to spectrally spread a 1 bit anti-duplication controlsignal must be sufficiently large. The PN code length per bit of theanti-duplication control signal may also be expressed as a spread gain(spread factor) which is the ratio (T/TC) of a time width T per bit ofthe anti-duplication control signal and a time width TC of one part (onechip) of the PN code. As described hereinafter, this spread gain isfound from the S/N ratio of the information signal on which theanti-duplication control signal is superimposed, in this case the SINratio of the video signal.

[0025] For example, when the S/N ratio of the video signal on which theanti-duplication control signal is superimposed is 50 dB, theanti-duplication control signal which is spectrally spread andsuperimposed on the video signal must be superimposed at a lower levelthan 50 dB, which is the S/N ratio of the video signal. Also, in orderto detect the anti-duplication control signal superimposed on the videosignal, its S/N ratio must be sufficient for the spectrally spreadsignal to be fully demodulated. If this S/N ratio is 10 dB, a spreadgain of 60 dB (S/N ratio of 50 dB for video signal)+(S/N ratio of 10 dBnecessary for detection) is required. In this case, the PN code lengthper bit of the anti-duplication control signal is 1 million.

[0026] The method used in the recording device to detect the PN codesuperimposed on the video signal uses a multifilter or a slidingcorrelation. In the former case, detection of the PN code is rapid, butonly a short code length can be detected. At present, this code lengthis of the order of 256, and when the PN code length is 1 million per bitof the anti-duplication control signal, it cannot be detected. In thelatter case, PN codes of long length can be detected but the detectiontakes time. It can thus be appreciated that a considerable time isrequired to detect a PN code having a length of 1 million.

[0027] Moreover, if the superposition level of the spectrally spreadanti-duplication control signal is too high, the anti-duplicationcontrol signal causes serious visual interference with the video signal.

[0028] This invention, in view of the above, aims to permit additionalinformation to be superimposed on a video signal so as to controlduplication of the signal without causing its deterioration, and tocontrol such duplication by precisely and rapidly extracting thisadditional information.

[0029] A video duplication control system according to this inventioncomprises a playback device for playing back a video signal, and arecording device for receiving the video signal output by the playbackdevice and recording it on a recording medium, wherein:

[0030] the playback device comprises:

[0031] sync signal separating means on the playback side for separatinga sync signal from the video signal,

[0032] spread code generating means on the playback side for generatinga spread code with a start timing based on the sync signal separated bysync signal separating means on the playback side,

[0033] spread code inverting means on the playback side for reversingthe phase of the spread code from spread code generating means on theplayback side with a timing based on the sync signal separated by theseparating means on the playback side,

[0034] spectrum spreading means for spectrally spreading duplicationcontrol information superimposed on the video signal according to thespread code processed by spread code inverting means on the playbackside, and

[0035] superimposing means for superimposing the duplication controlinformation which has been spectrally spread by the spectrum spreadingmeans on the video signal,

[0036] the recording means comprises:

[0037] sync signal separating means on the recording side for separatingthe sync signal from the video signal supplied by the playback means,

[0038] spread code generating means on the recording side for generatinga spread code with a start timing based on the sync signal separated bysync signal separating means on the recording side,

[0039] spread code inverting means on the recording side for reversingthe phase of the spread code from spread code generating means on therecording side with a timing based on the sync signal separated by theseparating means on the recording side,

[0040] reverse spectrum spreading means for performing reverse spectralspread according to the spread code processed by spread code invertingmeans on the recording side, and extracting the duplication controlinformation superimposed on the video signal supplied by the playbackdevice, and

[0041] duplication control means for controlling recording of the videosignal on the recording medium based on the duplication controlinformation extracted by the spectrum spreading means.

[0042] A video recording medium according to this invention ischaracterized in that a video signal on which additional information,which has been spectrally spread by a reverse spread code obtained byreversing, with a timing based on a sync signal in the video signal, thephase of a spread code which starts to be generated with a timing basedon the sync signal in the video signal and superimposed on the videosignal, is recorded on it.

[0043] In the duplication control system according to this invention, aspread code starts to be generated with a timing based on the syncsignal separated from the video signal in the playback device, and thespread code is phase inverted with a timing based on this sync signal.In this context, phase inversion of the spread code refers to bitinversion where 0's are replaced by 1's and 1's are replaced by 0's. Theadditional information is spectrally spread using this inverted spreadcode and superimposed on the video signal.

[0044] In the recording device, a spread code starts to be generatedwith a timing which is identical to the generation timing in theplayback device relative to the video sync signal and based on the videosync signal separated from the video signal supplied by the playbackdevice. Also, the polarity of the spread code generated in the recordingdevice is reversed with a timing based on the video sync signal. In therecording device, this inverse spread code is used to perform reversespectral spread.

[0045] During reverse spectral spread, the generation timing of thespread code used to perform reverse spectral spread must be controlledfor the video signal from the playback device so that it is identical tothat of the spread code used to perform spectral spread in the playbackdevice.

[0046] This generation timing is determined based on the video syncsignal separated from the video signal. The generation timing of thespread code generated in the recording device can therefore be adjustedto be the same as the generation timing of the spread code used in theplayback device for the video sync signal.

[0047] The spread code used to perform spectral spread in the playbackdevice and the spread code used to perform reverse spectral spread inthe recording device are phase inverted with a timing based on the videosync signal. For example, by inverting the polarity of the spread codeevery other field (one vertical interval), a spread code of differentpolarity in every field is generated.

[0048] In the recording device, similarly to the case of the spread codefor performing spread, reverse spectral spread is performed using thespread code for performing reverse spectral spread which has been phaseinverted such that, for example, its polarity is different in everyfield, and the additional information which has been spectrally spreadand superimposed on the video signal is detected.

[0049] During reverse spectral spread, the spread code which has beenarranged to have different polarity every field is applied to the videosignal comprising the spectrally spread anti-duplication control signal,and integrated. The anti-duplication control signal superimposed on thevideo signal is thereby extracted. In this case, by applying the spreadcode which has been arranged to have different polarity in every fieldto the playback signal, the polarity of the video signal components inthe playback signal is reversed every field.

[0050] The video signal is a signal having a high correlation betweenadjacent fields, between frames and between adjacent horizontal scanninglines. Therefore by performing integration as part of the process ofreverse spectral spread, video signal components of different polarityin adjacent fields cancel each other out, and are thereby eliminated.

[0051] In this way, the additional information which has been spectrallyspread and superimposed on the video signal may be detected withoutaffecting high level video signal components, and the detectionefficiency of additional information is improved. Moreover due to thisimproved detection efficiency of the additional information superimposedon the video signal, the spread gain may also be reduced.

[0052] When the polarity of the spread code is reversed with a timingbased on the video sync signal in the video signal as described above,the polarity (phase) of the additional information superimposed on thevideo signal is reversed according to the applied spread code. In thiscase, in a similar way to polarity reversal every field of the colorsub-carrier wave in the color video signal and polarity reversal betweenevery horizontal scanning period, in the additional informationsuperimposed on the video signal, brightness variations between adjacentadditional information of different polarity are reversed, so thevariations are averaged and therefore do not stand out. Consequently,visual interference of the reproduced video due to the superimposedadditional information is suppressed.

[0053] In the video duplication system according to this invention, thesuperposition level of spectrally spread additional information suppliedto the superimposing means of the playback device is adjusted by leveladjusting means.

[0054] Therefore when the effect of the additional informationsuperimposed on the video signal can be reduced, for example byinverting the polarity of the spread code or the like, the superpositionlevel of the additional information may be increased. By increasing thesuperposition level, the efficiency of detecting the additionalinformation in the recording device may be further improved.

[0055] Regarding the video recording medium according to this invention,in the recording device which receives the video signal played back fromthis video recording medium, by performing reverse spectral spread usinga spread code which starts with the same timing and of which the timingis inverted with the same timing relative to the video signal, as thatof the spread code used for spectral spread of the additionalinformation superimposed on the video signal recorded on the medium, theefficiency of detecting the additional information is improved asdescribed hereabove.

[0056] Further, the polarity of the spread code is reversed with atiming based on the video sync signal, and this inverted spread code isused for performing spectral spread. Hence as described hereabove, inthe additional information superimposed on the video signal, brightnessvariations between adjacent additional information of different polarityare averaged and do not stand out. Consequently, visual interference ofthe reproduced video due to the superposition of additional informationon the video signal is suppressed.

[0057] Therefore, even in the case of a recording medium on which avideo signal is recorded wherein spectrally spread additionalinformation is superimposed on the video signal to prevent improperduplication, a good quality video can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

[0058]FIG. 1 is a block diagram for the purpose of describing oneembodiment of a video playback device of a video duplication controlsystem according to this invention.

[0059]FIG. 2 is a block diagram for the purpose of describing oneembodiment of a video recording device of the video duplication controlsystem according to this invention.

[0060]FIG. 3 is a block diagram for the purpose of describing a typicalconstruction of a PN code generator shown in FIG. 1 and FIG. 2.

[0061]FIG. 4 is a diagram for the purpose of describing an example of aPN code start timing signal and inversion timing signal generated by thevideo playback device and video recording device shown in FIG. 1 andFIG. 2.

[0062]FIG. 5 is a diagram for the purpose of describing an example of aPN code generator.

[0063]FIG. 6 is a diagram for the purpose of describing another exampleof a PN code start timing signal and inversion timing signal generatedby the video playback device and video recording device shown in FIG. 1and FIG. 2.

[0064]FIG. 7 is a diagram for the purpose of describing another exampleof a PN code start timing signal and inversion timing signal generatedby the video playback device and video recording device shown in FIG. 1and FIG. 2.

[0065]FIG. 8 is a diagram for the purpose of describing an example of aPN code generator.

[0066]FIG. 9 is a block diagram for the purpose of describing anotherembodiment of the video playback device of the video duplication controlsystem according to this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0067] One embodiment of the video duplication control system, videoplayback device, video recording device, video transmitting method andvideo recording medium according to this invention will now be describedwith reference to the appended drawings. In the following description,it will be assumed that the video playback device and video recordingdevice are devices for the recording and playback of a DVD (DigitalVideo Disc), and are therefore hereafter referred to as DVD devices. Tosimplify the description, the audio signal system will be omitted.

[0068] As will be described in detail hereafter, in the videoduplication control system described below, an anti-duplication controlsignal is superimposed as additional information in the informationplayback device using a PN (Pseudorandom Noise) sequence code (PN code).This code is reverse spectrally spread in the information recordingdevice so as to extract the anti-duplication control signal which isused to control duplication of the video signal.

[0069] Embodiment 1

[0070]FIG. 1 and FIG. 2 are drawings for the purpose of describing avideo playback device (referred to hereafter simply as playback device)10 and a video recording device (referred to hereafter simply asrecording device) 20 used in a video duplication control systemaccording to the first embodiment. In other words, the playback device10 corresponds to the playback system of a DVD device, and the recordingdevice 20 corresponds to the recording system of a DVD device.

[0071] In FIG. 1, a recording medium 100 is a medium on which digitizedvideo and audio signals are recorded together with an anti-duplicationcontrol signal as additional information. In this case, the medium 100is a DVD. The anti-duplication control signal may be recorded on theinnermost or outermost TOC or a track area known as the directory, or itmay be inserted as a separate recording area on a track in which videodata or audio data is recorded. In the example described below thelatter case is discussed, the anti-duplication control signal being readout at the same time as the video signal is read.

[0072] The anti-duplication control signal is a signal for prohibitingor permitting duplication, or limiting the number of duplications, andit is added to the video signal. The recording medium 100 is fitted tothe playback device 10, and a recorded signal is read out.

[0073] As shown in FIG. 1, the playback device 10 comprises a read-outunit 11, demodulator, 12, anti-duplication control signal extractor 13,sync separator 14, PN code generator 15, PN code inverter 16, spectrallyspread anti-duplication control signal generator (referred to hereafteras SS anti-duplication control signal generator) 17, adder 18 and D/Aconversion circuits 191, 192.

[0074] The read-out unit 11 extracts a playback video signal componentS2 from the signal obtained by playing back the recording medium 100,and supplies this to the demodulator 12 and anti-duplication controlsignal extractor 13.

[0075] The demodulator 12 performs demodulation on the playback videosignal component S2, generates a digital video signal, and supplies thisto the D/A conversion circuit 191. The D/A conversion circuit 191performs D/A conversion on the digital video signal, generates an analogvideo signal S2A comprising a sync signal, and supplies the result tothe sync separator 14 and adder 18.

[0076] The anti-duplication control signal extractor 13 extracts ananti-duplication control signal S3 added to the playback video signalcomponent S2, and supplies the extracted anti-duplication control signalS3 to the SS anti-duplication control signal generator 17.

[0077] The sync separator 14 removes a video sync signal S4 from theanalog video signal S2A, and supplies the result to the PN codegenerator 15. According to the first embodiment, a vertical sync signalis extracted as the video sync signal S4, and supplied to the PN codegenerator 15.

[0078] The PN code generator 15 generates a PN code (spread code) usingthe vertical sync signal S4 as a reference and forms various timingsignals to be used in other processors.

[0079]FIG. 3 is a block diagram for describing the PN code generator 15of FIG. 1. As shown in FIG. 3, the PN code generator 15 comprises a PNcode start timing signal generator 151, PLL circuit 152, PN codegenerator 153 and timing signal generator 154. The vertical sync signalS4 extracted in the sync separator 14 is supplied to the PN code starttiming unit 151 of the PN code generator 15, the PLL circuit 152 and thetiming signal generator 154.

[0080] The PN code start timing signal generator 151 generates a PN codestart timing signal T1 (FIG. 4B) showing the timing at which the PN codestarts to be generated, based on the vertical sync signal S4 (FIG. 4A),and this is supplied to the PN code generator 153. The PN code starttiming signal T1 starts generation of the PN code every verticalinterval (1V in the figure), based on the vertical sync signal S4.

[0081] The PN code start timing signal T1 generated in the PN code starttiming unit 151 is used also as a timing signal in other processingunits.

[0082] The PLL circuit 152 generates a clock signal CLK based on thevertical sync signal S4 supplied to it, and the clock signal is suppliedto the PN code generator 153. The PLL circuit 152 generates a clocksignal CLK of which the frequency is 250 kHz, as described hereafter.

[0083] The PN code generator 153 determines the timing at which the PNcode starts to be generated by the PN code start timing signal T1,generates a PN code S5 according to this clock signal CLK, and outputsthe result.

[0084]FIG. 5 is a drawing showing an example of the PN code generator153 shown in FIG. 3. The PN code generator 153 in this example comprises12 flip-flops REG1-REG12 which form a 12 stage register, and exclusiveOFF circuits EX-OR1 to EX-OR3 for computing a suitable tap output ofthis register. When it receives the PN code start timing signal T1 as areset signal, the clock signal CLK and an enable signal EN, it generatesthe PN code S5 comprising 4095 chips per vertical interval.

[0085] In this case, when the clock rate is of the order of 250 kHz, oneperiod of the PN code is 4095/250=16.38 ms, so a 4095 chip PN code caneffectively be contained in one vertical interval (16.7 ms). Also, byusing the PN code start timing signal T1 as a reset signal, the clockphase of the PN code in every vertical interval can be specified.

[0086] The timing signal generator 154, in addition to various timingsignals based on the vertical sync signal S4, generates an inversetiming signal HT (FIG. 4C) used in the PN code inverter 16, describedhereafter, and supplies this signal to the PN code inverter 16.

[0087] The inverse timing signal HT is generated as a signal whichinverts every vertical interval, as shown in FIG. 4C.

[0088] Hence, the PN code generator 15 generates the PN code starttiming signal T1 using the vertical sync signal S4 as a referencesignal, the clock signal CLK and the inverse timing signal HT, andgenerates a PN code S5 based on the PN code timing signal T1 and clocksignal CLK. The PN code S5, clock signal CLK and inverse timing signalHT are supplied to the PN code inverter 16.

[0089] Based on the inverse timing signal HT, the PN code inverter 16controls whether or not to reverse the polarity (replacing 0 by 1 and 1by 0) of the PN code S5 in the PN code generator 15 and generates a PNinverse code S6. The inverse timing signal HT inverts every verticalinterval as described above, and the PN code inverting unit 16 reversesthe polarity of the PN code S5, for example in vertical intervals inwhich the inverse timing signal HT is high level. A PN inverse code S6is thereby supplied by the SS anti-duplication control signal generator17. The inverse timing signal HT may also be a phase as shown in FIG.4D, i.e. the polarity of the PN code can be reversed in either oddfields or even fields.

[0090] The SS anti-duplication control signal generator 17 spectrallyspreads the anti-duplication control signal S3 using the PN inverse codeS6 so as to generate a spectrally spread anti-duplication control signalS7, and supplies this to the D/A conversion circuit 192. The D/Aconversion circuit 192 converts the spectrally spread signal S7 to ananalog signal S7A, and supplies this to the adder 18.

[0091] The adder 18 adds the analog-converted spectrally spread signalS7A to the analog video signal S2A, and outputs a video signal S8A. Theadder 18 therefore functions as superimposing means for superimposingthe spectrally spread signal S7A, which is an anti-duplication controlsignal that has been spectrally spread by the PN inverse code S6, on theanalog video signal S2A.

[0092] The analog output video signal S8A, formed by superimposing thespectrally spread anti-duplication control signal on the analog videosignal, is then supplied to a monitor receiver which displays a video orto the recording device 20 records the video signal on a recordingmedium.

[0093] Next, the recording device 20 which receives the video signal S8Afrom the aforesaid playback device 10 and records it will be described.As shown in FIG. 2, the recording device 20 comprises an encoder 21,sync separator 22, PN code generator 23, PN code inverter 24, detector25 for detecting the anti-duplication control signal which has beenspectrally spread and superimposed on the video signal (referred tohereafter as SS anti-duplication control signal detector), duplicationcontroller 26 which performs control so as to permit or prohibitduplication, writer 27 and A/D conversion circuit 291. The recordingmedium 200 is a DVD on which the video signal is written by therecording device 20.

[0094] The video signal S8A from the playback device 10 is converted toa digital video signal S8 by the A/D conversion circuit 291, andsupplied to the encoder 21, sync separator 22 and SS anti-duplicationcontrol signal detector 25.

[0095] The encoder 21 receives the digital video signal S8, removes thevideo sync signal, and performs encoding operations such as datacompression of the digital video signal. This generates a digital videosignal S9 for recording which is supplied to the recording medium 200,and thence to the writer 27.

[0096] The sync separator 22 removes the video sync signal S11 from thedigital video signal S8 prior to encoding operations, and supplies it tothe PN code generator 23. In the recording device 20 also, a verticalsync signal is used as the video sync signal S11 as in theaforementioned playback device 10.

[0097] The PN code generator 23 has an identical construction to that ofthe PN code generator 15 of the playback device 10 which was describedreferring to FIG. 3, and is equivalent to the PN code start timingsignal generator 151, PLL circuit 152, PN code generator 153 shown inFIG. 5 and timing signal generator 154. The following descriptiontherefore assumes that the PN code generator 23 has the construction ofFIG. 3.

[0098] In the PN code generator 23, as in the PN code generator 15 ofthe aforesaid playback device 10, the PN code start timing signal T1which starts generation of the PN code every vertical interval, isgenerated by the PN code start timing signal generator 151, and a clocksignal CLK having a frequency of 250 kHz is generated by the PLL circuit152. The PN code start timing signal T1 and the clock signal CLK aresupplied to the PN code generator 153.

[0099] Using the PN code start timing signal T1 and the clock signalCLK, the PN code generator 153 generates the PN code S5 (S12 in FIG. 2).Specifically, the PN code S12 is generated with the same start timingand same generation rate relative to the video signal S8 as the PN codeS5 generated in the playback device 10.

[0100] The timing signal generator 154 of the PN code generator 23generates the inverse timing signal HT used in the PN code inverter 24.This inverse timing signal HT is a signal which is inverted everyvertical interval as described heretofore.

[0101] The PN code S12 and inverse timing signal HT generated in the PNcode generator 23 are supplied to the PN code inverter 24.

[0102] Similarly to the PN code inverter 16 of the playback device 10described hereabove, the PN code inverter 24 inverts the polarity of thePN code S12 supplied by the PN code generator 23 every other verticalinterval according to the inverse timing signal HT so as to generate aPN inverse code S13. The PN inverse code S13 is supplied to the SSanti-duplication control signal detector 25.

[0103] The SS anti-duplication control signal detector 25 functions asreverse spectral spread means. By performing reverse spectral spreadbased on the PN inverse code S13 as a reference signal, it extracts theanti-duplication control signal which has been spread and superimposedon the video signal S8, and supplies it to the duplication controller 26as an anti-duplication control signal S14.

[0104] Specifically, in the SS anti-duplication control signal detector25, reverse spectral spread is performed using the PN inverse code S13which is generated with the same start timing, same generation rate andsame inversion timing relative to the video signal S8 as the PN inversecode S6 used for spectral spread in the playback device 10.

[0105] In this reverse spectral spread, as described heretofore, theanti-duplication control signal superimposed on the video signal S8 isextracted by applying the PN inverse code S13 to the video signal S8comprising the spectrally spread anti-duplication control signal, andintegrating. According to this embodiment, the polarity of the videosignal S8 is reversed every vertical interval by applying the PN inversecode S13, of which the polarity is reversed every vertical interval, tothe video signal S8.

[0106] As described hereabove, the video signal is a signal having ahigh correlation between adjacent fields. Therefore, by performingintegration as part of the process of reverse spectral spread, videosignal components of different polarity in adjacent fields cancel eachother out, and are thereby eliminated.

[0107] By canceling out the high level video signal, theanti-duplication control signal which is spectrally spread and lowlevel, and which is superimposed on the video signal, can be preciselyand rapidly extracted. The anti-duplication control signal S14 extractedby the SS anti-duplication control signal detector 25 in this way issupplied to the duplication controller 26.

[0108] The duplication controller 26 decodes the anti-duplicationcontrol signal S14 and determines whether to prohibit or permitduplication. Based on this determination result, a write control signalS15 is generated and supplied to the write unit 27 so as to permit orprohibit writing of the video signal S9.

[0109] When the write control signal S15 permits writing, the write unit27 writes the video signal S9 on the recording medium 200, and when thewrite control signal prohibits writing, the write unit 27 does not writethe video signal S9 on the recording medium 200.

[0110] Hence, by starting generation of the PN code in every verticalinterval based on the vertical sync signal, generation of the PN codestarts with the same timing relative to the vertical sync signal in theplayback device 10 and recording device 20. In other words, based on thevideo sync signal, synchronism can be established between the PN codeused for spectral spread and the PN code used for reverse spectralspread.

[0111] Moreover, by using a PN code of reverse polarity to the PN codeevery vertical interval which has the same timing relative to the videosignal in both the playback device 10 and recording device 20, videosignal components are canceled out during reverse spectral spread in therecording device 20 as described hereabove, and the anti-duplicationcontrol signal which is spectrally spread and superimposed on the videosignal can be rapidly and precisely extracted. Consequently, theanti-duplication control signal S14 which is spectrally spread andsuperimposed on the video signal S8 is detected with higher efficiency,and the spread gain may be reduced.

[0112] By using a reverse PN code which has reverse polarity to the PNcode every other vertical interval, the polarity of the spectrallyspread anti-duplication control signal obtained by applying this PNreverse code is also reversed every vertical interval. The brightnessvariation of the superimposed anti-duplication control signal istherefore also reversed every field.

[0113] The brightness variation of anti-duplication control signals ofdifferent polarity superimposed on adjacent fields is therefore averagedout, so that anti-duplication control signal components do not stand outeven when the video signal on which the anti-duplication control signalis superimposed, is played back.

[0114] According to this first embodiment, the PN code start timingsignal T1 initiates the generation of the PN code every verticalinterval (one field) based on the vertical sync signal, but it may alsoinitiate the generation of the PN code every two vertical intervals (oneframe). Further, the inverse timing signal HT may be generated toreverse the polarity of the PN code every two vertical intervals.

[0115] Specifically, a PN code start timing signal T2 of two verticalperiods is generated in the PN code start timing signal generator 151 ofthe PN code generator 15 of the aforesaid playback device 10, and aninverse timing signal HT2 which inverts every two vertical periods isgenerated in the timing signal generator 154.

[0116] In the recording device 20, the PN code start timing signal T2 oftwo vertical periods is generated in the PN code generator 23constructed in the same way as the PN code generator 15 of the playbackdevice 10, and the inverse timing signal HT2 of two vertical periods isalso generated.

[0117]FIG. 6 shows an example of the PN code start timing signal T2 andthe inverse timing signal HT2. The PN code start timing signal T2 of twovertical periods which is generated with reference to the front edge ofthe vertical sync signal (FIG. 6A) may be as shown in FIG. 6B or FIG.6D. For the PN code start timing signal T2 of FIG. 6B, the inversetiming signal HT2 is as shown in FIG. 6C, and for the PN code starttiming signal T2 in FIG. 6D, the inverse timing signal HT2 is as shownin FIG. 6E. Signals having a reverse phase to those of the inversetiming signals HT2 of FIG. 6C or 6E are also respectively generated asinverse timing signals HT2 of two vertical periods, and may be used assuch.

[0118] By using the PN code start timing signals T2 shown in FIG. 6B,FIG. 6D, and the inverse timing signals HT2, spectral spread of theanti-duplication control signal, superimposing of the spectrally spreadanti-duplication control signal on the video signal and reverse spectralspread may be performed in processing units of one frame.

[0119] In this case, during reverse spectral spread in the SSanti-duplication control signal detector 25 of the recording device 20,the PN inverse code S13 which starts to be generated every two verticalintervals and of which the polarity is reversed every two verticalintervals, is applied to the video signal S8 comprising the spectrallyspread anti-duplication control signal. The polarity of the video signalS8 is therefore also reversed every two vertical intervals.

[0120] The video signal is a signal having a high correlation alsobetween adjacent frames as described hereabove, and video signalcomponents of different polarity in adjacent frames cancel each otherout during reverse spectral spread even when the PN code start timingsignal T2 of one frame period and the inverse timing signal HT2 of oneframe period are used. Consequently, the spectrally spreadanti-duplication control signal superimposed on the video signal S8 maybe precisely and rapidly extracted in the recording device 20 withoutbeing affected by video signal components.

[0121] By using the PN inverse code of which the polarity is reversedevery two vertical intervals, the polarity of the spectrally spreadanti-duplication control signal to which this PN code is applied is alsoreversed every two vertical intervals. Hence, the polarity of thesuperimposed anti-duplication control signal is reversed at everyadjacent frame, and the brightness variation of the superimposedanti-duplication control signal is reversed every two vertical intervals(one frame).

[0122] The brightness variation between superimposed anti-duplicationcontrol signals of different polarity is therefore averaged overadjacent frames, and it does not stand out even when the video signal onwhich the anti-duplication control signal is superimposed is playedback.

[0123] Moreover, the same effect is obtained when the PN code starttiming signal of two vertical intervals (one frame) and the inversetiming signal which inverts every two vertical intervals are used, aswhen the PN code start timing signal of one field period and the inversetiming signal which inverts every vertical interval are used.

[0124] When the timing signals T2 and HT2 of FIGS. 6D, E are used, videosignal components are canceled out by field correlation, and thebrightness variation of the anti-duplication control signal in theplayback video does not stand out.

[0125] Modification of Embodiment 1

[0126] In the aforesaid first embodiment, vertical sync signals are usedas the video sync signals S4, S11, but horizontal sync signals may alsobe used.

[0127] In this case, in the playback device 10 shown in FIG. 1, ahorizontal sync signal is extracted from the video signal, and this issupplied to the PN code generator 15 as the video sync signal S4.

[0128] As described hereabove, the PN code generator 15 is constructedas shown in FIG. 3. In the PN code start timing signal generator 151 ofthe PN code generator 15, a PN code start timing signal T3, which startsgeneration of the PN code every horizontal interval (referred tohereafter as 1H), is generated based on a horizontal sync signal S4.

[0129]FIG. 7 is a drawing for describing examples of the PN code starttiming signal T3 generated in the PN code start timing signal generator151 and an inverse timing signal HT3. FIG. 7B is an example of the PNcode start timing signal T3 which starts generation of the PN code every1H based on the front edge of the horizontal sync signal (FIG. 7A). FIG.7C is an example of the inverse timing signal HT3 in this case, which isa signal that inverts every 1H. In this case, the inverse timing signalHT3 may be a signal of reverse phase to the signal shown in FIG. 7.

[0130] In the case of this example, the clock signal CLK is generatedbased on the horizontal sync signal S4 as a reference signal in the PLLcircuit 152. This clock signal CLK is supplied to the PN code generator153. In this example, the PLL circuit 152 generates a clock signal CLKof which the frequency is, for example, 1 MHz.

[0131]FIG. 8 is a drawing showing an example of the PN code generator153 used in this case, comprising 6 D flip-flops REG1 to REG6 andexclusive OFF circuits EX-OR. The PN code generator shown in FIG. 8receives the PN code start timing signal T3 as a reset signal, the clocksignal CLK and an enable signal EN, and generates a PN code of 63 chipsper 1H.

[0132] In this case when the clock rate is 1 MHz, one period of the PNcode is 63/1=63 μs, so a 63 chip PN code is generated in effectively onehorizontal scanning interval (63.5 μs). Also by using for example the PNcode start timing signal T3 as a reset signal, the phase of the PN codeevery 1H can be specified.

[0133] In the timing signal generator 154, the inverse timing signal HTand various other timing signals are generated using the horizontal syncsignal as a reference signal. In this example the timing signalgenerator 154 generates the inverse timing signal HT3 which reverses thepolarity of the PN code every 1H in the same way as the PN code starttiming signal T3.

[0134] Therefore, in the playback device 10, the anti-duplicationcontrol signal S3 is spectrally spread using the PN inverse code S6which starts to be generated every 1H and of which the polarity isreversed every 1H as a reference signal, and the PN inverse code S6 issuperimposed on the video signal.

[0135] Likewise, in the recording device 20 shown in FIG. 2, thehorizontal sync signal is extracted from the video signal by the syncseparator 22, and is supplied to the PN code generator 22 using theextracted horizontal sync signal as the video sync signal S11.

[0136] The PN code generator 22 of this recording device 20 isconstructed in the same way as the PN code generator 15 of the playbackdevice 10. It generates the PN code start timing signal T3 which startsgeneration of the PN code S12 every 1H, a clock signal CLK of frequency1 MHz, and the inverse timing signal HT3 which reverses the phase of thePN code S12 every 1H in the same way as the PN code generation timingsignal T3.

[0137] Therefore in the recording device 20, reverse spectral spread isperformed using the PN inverse code S13 which starts to be generatedevery 1H and of which the polarity is reversed every 1H, and aspectrally spread anti-duplication control signal which is superimposedon the video signal is extracted.

[0138] When the PN code S5 starts to be generated every 1H and thepolarity of the PN code S5 is reversed every 1H in the playback device10, the PN code S12 starts to be generated every 1H and the polarity ofthe PN code S12 is reversed every 1H in the recording device 20. Thestart timing (clock phase) of the PN inverse codes S6, S13 generated inthe playback device 10 and recording device 20 is therefore applied tothe video signal every 1H.

[0139] During reverse spectral spread in the recording device 20,reverse spectral spread is performed by applying the PN inverse code S13to the video signal S8 from the playback device 10. During this reversespectral spread, as described heretofore, by applying the PN inversecode S13 to the video signal S8 comprising the spectrally spreadanti-duplication control signal and integrating, the anti-duplicationcontrol signal superimposed on the video signal can be extracted.

[0140] By applying this PN inverse code signal S13 to the video signalS8, the polarity of the video signal S8 is also reversed every 1H. Thevideo signal is a signal having a high correlation also between adjacenthorizontal intervals. During the integration process in reverse spectralspread, video signal components in adjacent horizontal intervals inwhich the polarity is reverses, cancel each other out and areeliminated. The anti-duplication control signal superimposed on thevideo signal may therefore be extracted without being affected by videosignal components.

[0141] As video signal components can be canceled out during reversespectral spread even when the PN code start timing signal T1 and theinverse timing signal HT are generated based on the horizontal syncsignal, the anti-duplication control signal which is spectrally spreadand superimposed on the video signal can be precisely and rapidlyextracted without being affected by video signal components.

[0142] As described hereabove, the polarity of the PN inverse code S13is inverted every 1H. By applying this inverse code, the phase of theanti-duplication control signal is also reversed every 1H, andconsequently brightness variations of the anti-duplication controlsignal superimposed on the video signal are averaged out over adjacenthorizontal intervals. The superimposed anti-duplication control signaltherefore does not stand out and there is no video deterioration evenwhen the video signal on which the anti-duplication control signal issuperimposed is played back.

[0143] According to this embodiment, the PN code start timing signal T3was generated as a signal having a period of 1H, but it may also have aperiod of two horizontal intervals (referred to hereafter as 2H).

[0144] In FIG. 7, FIG. 7D and FIG. 7E both show an example of the PNcode start timing signal T3 which starts PN code generation every 2H. Inthis case, the signals having reverse phase shown in FIG. 7E and FIG. 7Gmay also respectively be used as the corresponding inverse timing signalHT3.

[0145] Hence, even when the horizontal sync signal is used as areference, the efficiency of detecting the spectrally spreadanti-duplication control signal superimposed on the video signal can beimproved, and as visual interference due to superposition of theanti-duplication control signal on the video signal when the videosignal is played back does not stand out, the spread gain can bereduced. As a result, the same effect is obtained when the horizontalsync signal is used as a reference signal as when the vertical syncsignal is used as a reference signal.

[0146] Embodiment 2

[0147] Next, a video duplication control system and video playbackdevice according to a second embodiment of this invention will bedescribed.

[0148]FIG. 9 is a block diagram for the purpose of describing a playbackdevice used in a video duplication control system according to thesecond embodiment. As the recording device in the video duplicationcontrol system according to the second embodiment, the recording device20 according to the aforesaid first embodiment is used.

[0149] As shown in FIG. 9, the playback device 30 according to thesecond embodiment comprises the read-out unit 11, decoder 12,anti-duplication control signal extractor 13, sync separator 14, PN codegenerator 15, PN code inverter 16, SS anti-duplication control signalgenerator 17, adder 18 and D/A conversion circuits 191, 192, as in thecase of the playback device 10 according to the aforesaid firstembodiment. In the playback device 30 according to the secondembodiment, a level controller 19 is provided between the SSanti-duplication control signal generator 17 and adder 18.

[0150] Apart from the level controller 19, the playback device 30operates in the same way as the aforesaid playback device 10. Therefore,in the playback device 30 according to the second embodiment, when thevertical sync signal is used as the video sync signal S4, the PN code S5is generated every vertical interval and the PN inverse code S6 in whichthe polarity of the PN code S5 is reversed is generated every verticalinterval, as in the case of the aforesaid playback device 10. This isused to perform spectral spread of the anti-duplication control signalS3 extracted by the anti-duplication control signal extractor.

[0151] This spectrally spread signal S7 is D/A converted, and thepolarity of the video signal component is reversed every verticalinterval during reverse spectral spread in the recording device 20 bysupplying the video signal S8A, produced by superposition on the analogvideo signal S2A, to the recording device 20. Image signal componentsare canceled out due to interfield correlation in the video signal.

[0152] Therefore in the recording device 20, as described hereabove, theefficiency of detecting the anti-duplication control signal superimposedon the video signal is improved, and the spread gain maybe reduced.Also, the anti-duplication control signal superimposed on the videosignal does not cause deterioration of the video signal.

[0153] When the anti-duplication control signal superimposed on thevideo signal causes little deterioration of the video signal, thesuperposition level of the spectrally spread anti-duplication controlsignal may be increased within such limits that the video signal is notdeteriorated.

[0154] The playback device 30 of the second embodiment thereforecomprises the level adjuster 19 as shown in FIG. 9 so that thesuperposition level of the spectrally spread signal S7A superimposed onthe analog video signal S2A may be increased.

[0155] In the level adjuster 19 of the playback device 30, when aspectrally spread signal S7A of high level is superimposed on the analogvideo signal S2A, the efficiency of detecting the anti-duplicationcontrol signal in the recording device 20 is further improved.

[0156] According also to this second embodiment, generation of the PNcode may be started every 2V, and the polarity of the PN code may bereversed every 2V.

[0157] According to this second embodiment, a vertical sync signal wasused as the video sync signal S4, however it will be understood that ahorizontal sync signal may also be used instead.

[0158] According to the aforesaid first and second embodiments, theanti-duplication control signal added to the video signal on therecording medium 100 is extracted, this is spectrally spread using thePN inverse code S6, and the result is superimposed on the video signalsupplied to the recording device, however a recording medium on which aspectrally spread anti-duplication control signal has been previouslysuperimposed may also be used.

[0159] In the case of a recording medium on which a spectrally spreadanti-duplication control signal has been previously superimposed, thereis no need to extract the anti-duplication control signal, performspectral spread and superimpose the spectrally spread anti-duplicationcontrol signal on the video signal as in the aforesaid playback devices10, 30, it being sufficient to play back the recording medium to outputthe video signal.

[0160] In this case, in the recording device 20, reverse spectral spreadis performed using a PN inverse code which starts to be generated at thesame rate with the same timing, and of which the polarity is reversedwith the same timing, as the PN inverse code used for spectral spread ofthe anti-duplication control signal which was previously superimposed onthe video signal recorded on the recording medium.

[0161] Hence, even when a recording medium is used on which a spectrallyspread anti-duplication control signal has been previously superimposed,the anti-duplication control which is spectrally spread and superimposedon the video signal can be extracted, and duplication controlledaccording to the anti-duplication control signal.

[0162] An anti-duplication control signal generator may also be providedin the playback device, and an anti-duplication control signal generatedin the playback device spectrally spread using the PN inverse code andsuperimposed on the output video signal, as described hereabove.

[0163] In this case, when an anti-duplication control signal is notrecorded on the recording medium or when the spectrally spreadanti-duplication control signal is not superimposed, duplication controlin the recording device may be performed using an anti-duplicationcontrol signal which has been generated in the playback device andsuperimposed on the output video signal.

[0164] According to the aforesaid first and second embodiments, the PNcode generation start timing and PN code polarity inversion timing weredescribed as every vertical interval or every two vertical intervals,but the invention is not limited to this arrangement. Various timingsmay be used based on the vertical sync signal, for example everyfractional part of a vertical interval such as every ½ or every ¼ of avertical interval, or every integral multiple of a vertical intervalsuch as every three or four vertical intervals.

[0165] Likewise, when a horizontal sync signal is used as the video syncsignal, the PN code generation start timing and PN code polarityreversal timing may be an integral multiple of a horizontal intervalsuch as every 1H, every 2H or every 3H, or a fractional part of ahorizontal interval such as ½H or ⅓H.

[0166] Further, the spectrally spread anti-duplication control signalsuperimposed timing may also be inserted intermittently such as everyother vertical interval or every two vertical intervals. Moreover, aplurality of information such as information to permit or prohibitduplication, or information for controlling the number of duplications,may be inserted alternately every 1V or every 2V. It will be understoodthat when a horizontal sync signal is used, information may likewise beinserted intermittently every other 1H or 2H, or a plurality ofinformation inserted alternately every 1H or 2H.

[0167] The positional relationships between the video sync signal, thePN code generation start timing and the timing with which polarity isreversed may be freely altered as desired. For example, according to theaforesaid first embodiment, the PN code start timing signal T1 andinverse timing signal HT were generated based on the front edge of thevertical sync signal, however the PN code start timing signal T1 andinverse timing signal HT may be generated based on a position removed bya predetermined number of blocks from the front edge of the video syncsignal.

[0168] Also, the positional relationship between the PN code starttiming signal and PN code inversion timing signal may be unique, ortheir phases may be reversed, or alternatively they may be madeindependent so that the PN code start timing T1 has a period of 1V andthe inverse timing signal HT has a period of 2V.

[0169] It is also possible to construct a video signalrecording/playback device incorporating the functions of both theplayback device 10 and recording device 20. In this case, the syncseparators 14, 22 and PN code generators 15, 24 may be constructed sothat they are shared by the playback system 30 and recording system 20.Alternatively, a video signal recording/playback device may beconstructed having the functions of both the playback device 30 andrecording device 20.

[0170] The aforesaid first and second embodiments were described for thecase of analog connections, wherein analog video signals were suppliedfrom the playback devices 10, 30 to the recording device 20, howeverthis invention may be applied also to the case of digital connections.

[0171] Further, in the aforesaid first and second embodiments, theplayback and recording devices were described in the context of theirapplication to a DVD device, however the invention is not limited tothis case. It may for example be applied to a VTR, digital VTR, videodisc, or video CD playback device and recording device. The inventionmay also be applied both to analog instruments such as an analog VTR ordigital instruments such as a DVD device.

[0172] In the aforesaid first and second embodiments, the followingprocedure may be followed instead of using the PN inverse code of whichthe polarity is reversed with a timing based on the video sync signal.

[0173] For example, the spectrally spread anti-duplication controlsignal may be superimposed every other field of the video signal. Inthis case during reverse spectral spread in the recording device, afterapplying a PN code, having the same generation timing and generationrate as the PN code used for spectral spread in the playback device, tothe video signal on which the spectrally spread anti-duplication controlsignal is superimposed, the video signal in a field on which theanti-duplication control signal is not superimposed is subtracted fromthe video signal in an adjacent field on which the anti-duplicationcontrol signal is superimposed.

[0174] Image signal components in adjacent fields (vertical intervals)having a high correlation are thereby canceled out, and theanti-duplication control signal superimposed on the video signal may beefficiently extracted. It will be understood that this subtraction mayalso be performed between adjacent frames or between adjacent horizontalintervals (horizontal lines).

[0175] As described hereabove, in the video duplication control system,video playback device and video recording device according to thisinvention, a spread code is generated with a timing based on a videosync signal, so spread codes can start to be generated with the sametiming relative to the video signal in the playback device and recordingdevice. Reverse spectral spread may thus be performed rapidly in therecording device.

[0176] Also, as the polarity of the spread code is reversed with atiming based on the video sync signal, the polarity of the video signalis reversed according to the polarity reversal of the spread code duringthe process of reverse spectral spread. As a result, video components inadjacent horizontal scanning lines, fields or frames having reversedpolarity are canceled out during reverse spectral spread, so additionalinformation superimposed on the video signal may be efficientlydetected.

[0177] Hence, the efficiency of detecting spectrally spread additionalinformation superimposed on the video signal is improved, and as theefficiency of detecting additional information is improved, the spreadgain may be reduced.

[0178] Further, by using a spread code of which the polarity is reversedwith a timing based on the video sync signal, the polarity of thespectrally spread additional information to which this spread code isapplied is also reversed with a timing based on the video sync signal.As a result, as the polarity of the anti-duplication control signalsuperimposed on adjacent horizontal intervals or vertical intervals isdifferent, the brightness variation of the additional information isaveraged, and the video signal does not deteriorate even when theadditional information is superimposed on it.

[0179] As the additional information superimposed on the video signalcauses little deterioration of the video signal, the superposition levelof the spectrally spread additional information may be increased.Consequently, when the superposition level is increased, the efficiencyof detecting the additional information in the recording device may befurther improved.

What is claimed is:
 1. A video duplication control system comprising aplayback device for playing back a video signal, and a recording devicefor receiving said video signal output by said playback device andrecording it on a recording medium, said playback device comprising:first sync signal separating means for separating a sync signal fromsaid video signal, first spread code generating means on the playbackside for generating a spread code with a start timing based on said syncsignal separated by said first sync signal separating means first spreadcode inverting means for reversing the phase of said spread code fromsaid first spread code generating means with a timing based on said syncsignal separated by said first sync signal separating means, spectrumspreading means for spectrally spreading duplication control informationsuperimposed on said video signal according to said spread codeprocessed by said first spread code inverting means, and superimposingmeans for superimposing said duplication control information which hasbeen spectrally spread by said spectrum spreading means on said videosignal, said recording means comprising: second sync signal separatingmeans for separating said sync signal from said video signal supplied bysaid playback means, second spread code generating means on therecording side for generating a spread code with a start timing based onsaid sync signal separated by said second sync signal separating means,second spread code inverting means for reversing the phase of saidspread code from said second spread code generating means with a timingbased on said sync signal separated by said second sync signalseparating means, reverse spectrum spreading means for performingreverse spectral spread according to said spread code processed by saidsecond spread code inverting means, and extracting said duplicationcontrol information superimposed on said video signal supplied by saidplayback device, and duplication control means for controlling recordingof said video signal on said recording medium based on said duplicationcontrol information extracted by said spectrum spreading means.
 2. Avideo duplication control system as claimed in claim 1, furthercomprising level adjusting means for adjusting the level of saidduplication control information which has been spectrally spread in saidspectrum spreading means and supplied to said superimposing means.
 3. Avideo duplication control system as claimed in claim 1, wherein saidsync signal separated from said video signal by said first and secondsync signal separating means is a vertical sync signal.
 4. A videoduplication control system as claimed in claim 1, wherein said syncsignal separated from said video signal by said first and second syncsignal separating means is a horizontal sync signal.
 5. A videoduplication control system as claimed in claim 1, wherein saidduplication control information is information which prohibits orpermits recording of said video signal on said recording medium, orrestricts the number of times said recording can be performed.
 6. Avideo duplication control system as claimed in claim 1, wherein saidfirst and second spread code generating means comprises start timingsignal generating means for generating a start timing signal having aperiod based on said sync signal, clock signal generating means forgenerating a clock signal synchronized with said sync signal, inversetiming signal generating means for generating an inverse timing signalhaving a period based on said sync signal, and spread code generatingmeans for generating a spread code in response to said clock signal witha timing based on said start timing signal, wherein said spread codereversing means reverses the phase of said spread code in response tosaid inverse timing signal.
 7. A video playback device comprising: syncsignal separating means for separating a sync signal from a videosignal, spread code generating means f or generating a spread code witha start timing based on said sync signal separated by sync signalseparating means, spread code inverting means for reversing the phase ofsaid spread code from said spread code generating means with a timingbased on said sync signal separated by said sync signal separatingmeans, spectrum spreading means for spectrally spreading duplicationcontrol information superimposed on said video signal according to saidspread code processed by said spread code inverting means, andsuperimposing means for superimposing said duplication controlinformation which has been spectrally spread by said spectrum spreadingmeans on said video signal.
 8. A video playback device as claimed inclaim 3, further comprising level adjusting means for adjusting thelevel of said duplication control information which has been spectrallyspread in said spectrum spreading means and supplied to saidsuperimposing means.
 9. A video playback device as claimed in claim 7,wherein said sync signal separated from said video signal by said sync.signal separating means is a vertical sync signal.
 10. A video playbackdevice as claimed in claim 7, wherein said sync signal separated fromsaid video signal by said sync signal separating means is a horizontalsync signal.
 11. A video playback device as claimed in claim 7, whereinsaid duplication control information is information which prohibits orpermits recording of said video signal on said recording medium, orrestricts the number of times said recording can be performed.
 12. Avideo playback device as claimed in claim 7, wherein said spread codegenerating means comprises start timing signal generating means forgenerating a start timing signal having a period based on said syncsignal, clock signal generating means for generating a clock signalsynchronized with said sync signal, inverse timing signal generatingmeans for generating an inverse timing signal having a period based onsaid sync signal, and spread code generating means for generating aspread code in response to said clock signal with a timing based on saidstart timing signal, wherein said spread code reversing means reversesthe phase of said spread code in response to said inverse timing signal.13. A video recording device for recording a video signal on whichduplication control information is superimposed which has beenspectrally spread according to a spread code generated with a timingbased on a sync signal in said video signal, comprising: sync signalseparating means for separating said sync signal from said video signal,spread code generating means for generating a spread code with a starttiming based on said sync signal separated by said sync signalseparating means, spread code inverting means for reversing the phase ofsaid spread code from said spread code generating means with a timingbased on said sync signal separated by said separating means, reversespectrum spreading means for performing reverse spectral spreadaccording to said spread code processed by said spread code invertingmeans on the recording side, and extracting said duplication controlinformation superimposed on said video signal, and duplication controlmeans for controlling recording of said video signal on a recordingmedium based on said duplication control information extracted by saidspectrum spreading means.
 14. A video recording device as claimed inclaim 13, wherein said sync signal separated from said video signal bysaid sync signal separating means is a vertical sync signal.
 15. A videorecording device as claimed in claim 13, wherein said sync signalseparated from said video signal by said sync signal separating means isa horizontal sync signal.
 16. A video recording device as claimed inclaim 13, wherein said duplication control information is informationwhich prohibits or permits recording of said video signal on saidrecording medium, or restricts the number of times said recording can beperformed.
 17. A video recording device as claimed in claim 13, whereinsaid spread code generating means comprises start timing signalgenerating means for generating a start timing signal having a periodbased on said sync signal, clock signal generating means for generatinga clock signal synchronized with said sync signal, inverse timing signalgenerating means for generating an inverse timing signal having a periodbased on said sync signal, and spread code generating means forgenerating a spread code in response to said clock signal with a timingbased on said start timing signal, wherein said spread code reversingmeans reverses the phase of said spread code in response to said inversetiming signal.
 18. A video recording medium, wherein a video signal onwhich additional information, which has been spectrally spread by areverse spread code obtained by reversing, with a timing based on a syncsignal in said video signal, the phase of a spread code which starts tobe generated with a timing based on said sync signal in said videosignal and has been superimposed on said video signal, is recorded onit.
 19. A video transmitting method for superimposing a spectrallyspread anti-duplication control signal on an analog video signal, andtransmitting the result, wherein: a spread code is generated which isrepeated with a period synchronized with a sync signal in said videosignal, and an inverse spread code is generated wherein the phase ofsaid spread code is reversed with a timing based on said sync signal insaid video signal, and said anti-duplication control signal isspectrally spread using said inverse spread code.
 20. An informationsuperimposing and extracting system comprising an informationsuperimposing device for superimposing additional information on a videosignal, and an information extracting device for extracting saidadditional information from said video signal, wherein said informationsuperimposing device comprises: first sync signal separating means forseparating a sync signal from said video signal, first spread codegenerating means for generating a spread code with a start timing basedon said sync signal separated by said first sync signal separatingmeans, first spread code inverting means for reversing the phase of saidspread code from said first spread code generating means with a timingbased on said sync signal separated by said first sync signal separatingmeans, spectral spread means for spectrally spreading said additionalinformation superimposed on said video signal according to said spreadcode processed by said first spread code inverting means, andsuperimposing means for superimposing said additional informationspectrally spread by said spectral spread means on said video signal,and wherein said information extracting means comprises: second syncsignal separating means for separating a sync signal from the videosignal supplied by said information superimposing device, second spreadcode generating means for generating a spread code with a start timingbased on said sync signal separated by said second sync signalseparating means, second spread code inverting means for reversing thephase of said spread code from said second spread code generating meanswith a timing based on said sync signal separated by said second syncsignal separating means, and reverse spectral spread means forperforming reverse spectral spread according to said spread codeprocessed by said second spread code inverting means, and extractingsaid additional information superimposed on said video signal suppliedby said information superimposing means.
 21. An information extractingdevice for extracting additional information from a video signal onwhich said additional information, which has been spectrally spreadaccording to a spread code generated with a start timing based on a syncsignal in said video signal, has been superimposed, comprising: syncsignal separating means for separating a sync signal from said videosignal, spread code generating means for generating a spread code with astart timing based on said sync signal separated by said sync signalseparating means, spread code inverting means for reversing the phase ofsaid spread code from said spread code generating means with a timingbased on said sync signal separated by said sync signal separatingmeans, and reverse spectral spread means for performing reverse spectralspread according to said spread code processed by said spread codeinversion means, and extracting said additional information superimposedon said video signal.